Power over Ethernet (PoE) is a technology which enables power transmission through Ethernet cabling. There are several techniques for implementing PoE and IEEE 802.3af or IEEE 802.3at is two examples of standards for implementing PoE. In the IEEE standards there are two modes or alternatives for implementing PoE, one where the power is transmitted on unused conductors of the Ethernet cable and one where the power is transmitted on conductors also used for transmitting data. This allows a single Ethernet cable to provide both data connection and electrical power to powered devices (PD). In other words, when the PD is provided with PoE, the PD can be connected to the cables to work normally without coupling to a separate power socket. The above-mentioned function of PoE is very convenient. However, depending on the PoE standard used, and also depending on the type of power source equipment (PSE) used for delivering the power over the cables, a plurality of different input powers (PoE classes) may be available for the PD.
An example of a PD is an amplifying device for increasing the power of a signal, e.g. an audio signal. Normally, such an amplifying device is configured for a certain input power, e.g. 40W or 25W. If an amplifying device that is configured for an input power of 40W is fed with 25W, the signal quality will be affected and the user will not be able to control the output signal in an intuitive way with a control interface. This implies that different product versions of the amplifying device are needed for each PoE class to match the available input power.
This is inconvenient for the manufacturer of such PD:s, since a plurality of product versions are needed in order to support different classes of PoE. Moreover, it is inconvenient for the user of the PD, since the user needs to be aware of what PoE-class that is delivered from the PSE of his/hers network infrastructure.